The capacity of greening roof to reduce stormwater runoff and pollution

•The green roof could effective reduce stormwater runoff.•A key factor affecting runoff retention was the depth of rainfall.•The green roof acted as a sink of NH4+-N and could neutralize the pH of rainfall.•The water quality of runoff was seriously affected by the soil substrate of the green roof.•The green roof was effective in abating the loading of most pollutants.